Multiple drive axle assemblies, such as tandem axles, having interaxle differentials, also called power dividers, with selectively engaged interaxle and wheel differential lockups, and the mechanisms and controls for selectively locking said differentials, are well known in the prior art as may be seen by reference to U.S. Pat. Nos. 3,000,456 and 3,388,760, the disclosures of which are hereby incorporated by reference in their entirety.
Multi-speed tandem axles having lockable interaxle differentials with separate controls for selectively shifting the axles and engaging the interaxle differential, and controls for limiting shifting of the axles in response to sensing engagement of the interaxle differential lockup are known in the prior art as may be seen by reference to U.S. Pat. No. 3,368,638, the disclosure of which is hereby incorporated by reference in its entirety.
As may be seen by reference to U.S. Pat. No. 4,432,431, also hereby incorporated by reference in its entirety, differential lock assemblies typically include a push or a piston rod member slidably mounted within a shift cylinder. A shift fork member is fixedly connected to the piston rod member in a substantially perpendicular relationship. The shift fork member rotatably engages a slidable clutch member which has a splined bore. The splined bore of the slidable clutch member slidably engages a splined shaft member. The piston member is biased by a spring such that the sliding clutch is disengaged from a fixed clutch. When the piston member is biased by the spring to a position where the sliding clutch is disengaged from the fixed clutch, the differential is rendered operable. However, upon pressure being delivered to the shift cylinder, the piston rod, and correspondingly the shift fork and sliding clutch, will be moved such that the sliding clutch is lockably engaged with the fixed clutch thereby locking out the differential.
Of course, as set forth in U.S. Pat. No. 4,432,431, a reverse bias system may also be provided in which the piston rod is spring biased such that the sliding clutch is in locking engagement with the fixed clutch. In such a system, the sliding clutch would be displaced from locking engagement with the fixed clutch by the application of pressure to the shift cylinder.
While other components may and generally do comprise a complete differential lockup system, such parts, a number of which are described in U.S. Pat. No. 4,432,431, are well known in the art and will not be described in further detail here.
Differential lock systems typically provide some sort of adjustment to ensure that the shift fork is not binding or continuously rubbing against the sliding clutch when the sliding clutch is in the engaged position with the fixed clutch. Such adjustments are necessary to account for tolerance stackups which occur during assembly between the parts incorporated within the differential lock system. Adjustments are also necessary to account for the differential bearing preload and to set the backlash in a bevel gear set.
For example, the shift fork may be connected to the piston rod via a clinch bolt. This allows the shift fork to be adjusted axially along the piston rod before being fixedly connected via the clinch bolt. Thus, after the differential lock system has been assembled, and in order to account for tolerance stackups and bearing or gear settings, a feeler gauge may be placed between the sliding clutch and the fixed clutch in a disengaged position and the clutch bolt tightened to fixedly connect the shift fork to the piston rod in the correct axial position.
Alternatively, the piston member may include a threaded portion which may be threadably engaged to a threaded sleeve having limited axial movement within the shift cylinder. The shift fork is adjusted axially along the piston rod by rotating the piston rod such that the threaded portion of the piston rod engages the threaded sleeve thereby moving the piston rod axially in the direction desired. The piston rod can then be locked into place axially via a jam lock set screw.
Because such ways of adjusting the axial position of the shift fork are well known in the art, will not be described in further detail here. The problem with such typical adjustment systems is that they require the shift fork to be adjusted after the differential lock system has been assembled.